[PATCH v2] hamradio: replace deprecated strncpy with strscpy_pad

[PATCH v2] hamradio: replace deprecated strncpy with strscpy_pad

[Justin Stitt]

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect both hi.data.modename and hi.data.drivername to be
NUL-terminated based on its usage with sprintf:
|       sprintf(hi.data.modename, "%sclk,%smodem,fclk=%d,bps=%d%s",
|               bc->cfg.intclk ? "int" : "ext",
|               bc->cfg.extmodem ? "ext" : "int", bc->cfg.fclk, bc->cfg.bps,
|               bc->cfg.loopback ? ",loopback" : "");

Note that this data is copied out to userspace with:
|       if (copy_to_user(data, &hi, sizeof(hi)))
... however, the data was also copied FROM the user here:
|       if (copy_from_user(&hi, data, sizeof(hi)))

Considering the above, a suitable replacement is strscpy_pad() as it
guarantees NUL-termination on the destination buffer while also
NUL-padding (which is good+wanted behavior when copying data to
userspace).

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Changes in v2:
- use strscpy_pad (thanks Kees)
- bytes arrays are now considered "buffets" :) (thanks Kees)
- Link to v1: https://lore.kernel.org/r/20231012-strncpy-drivers-net-hamradio-baycom_epp-c-v1-1-8f4097538ee4@google.com
---
Note: build-tested only.

Also, there are 33 instances of trailing whitespace in this file alone.
I've opted to not remove them in this patch.
---
 drivers/net/hamradio/baycom_epp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
index 83ff882f5d97..ccfc83857c26 100644
--- a/drivers/net/hamradio/baycom_epp.c
+++ b/drivers/net/hamradio/baycom_epp.c
@@ -1074,7 +1074,7 @@ static int baycom_siocdevprivate(struct net_device *dev, struct ifreq *ifr,
 		return 0;
 
 	case HDLCDRVCTL_DRIVERNAME:
-		strncpy(hi.data.drivername, "baycom_epp", sizeof(hi.data.drivername));
+		strscpy_pad(hi.data.drivername, "baycom_epp", sizeof(hi.data.drivername));
 		break;
 		
 	case HDLCDRVCTL_GETMODE:
@@ -1091,7 +1091,7 @@ static int baycom_siocdevprivate(struct net_device *dev, struct ifreq *ifr,
 		return baycom_setmode(bc, hi.data.modename);
 
 	case HDLCDRVCTL_MODELIST:
-		strncpy(hi.data.modename, "intclk,extclk,intmodem,extmodem,divider=x",
+		strscpy_pad(hi.data.modename, "intclk,extclk,intmodem,extmodem,divider=x",
 			sizeof(hi.data.modename));
 		break;
 

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231012-strncpy-drivers-net-hamradio-baycom_epp-c-6e11c9483b9f

Best regards,
--
Justin Stitt <justinstitt@google.com>

Re: [PATCH v2] hamradio: replace deprecated strncpy with strscpy_pad

[Kees Cook]

On Mon, Oct 16, 2023 at 06:42:42PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> We expect both hi.data.modename and hi.data.drivername to be
> NUL-terminated based on its usage with sprintf:
> |       sprintf(hi.data.modename, "%sclk,%smodem,fclk=%d,bps=%d%s",
> |               bc->cfg.intclk ? "int" : "ext",
> |               bc->cfg.extmodem ? "ext" : "int", bc->cfg.fclk, bc->cfg.bps,
> |               bc->cfg.loopback ? ",loopback" : "");
> 
> Note that this data is copied out to userspace with:
> |       if (copy_to_user(data, &hi, sizeof(hi)))
> ... however, the data was also copied FROM the user here:
> |       if (copy_from_user(&hi, data, sizeof(hi)))
> 
> Considering the above, a suitable replacement is strscpy_pad() as it
> guarantees NUL-termination on the destination buffer while also
> NUL-padding (which is good+wanted behavior when copying data to
> userspace).
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Thanks!

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH v2] hamradio: replace deprecated strncpy with strscpy_pad

[Simon Horman]

On Mon, Oct 16, 2023 at 12:42:22PM -0700, Kees Cook wrote:
> On Mon, Oct 16, 2023 at 06:42:42PM +0000, Justin Stitt wrote:
> > strncpy() is deprecated for use on NUL-terminated destination strings
> > [1] and as such we should prefer more robust and less ambiguous string
> > interfaces.
> > 
> > We expect both hi.data.modename and hi.data.drivername to be
> > NUL-terminated based on its usage with sprintf:
> > |       sprintf(hi.data.modename, "%sclk,%smodem,fclk=%d,bps=%d%s",
> > |               bc->cfg.intclk ? "int" : "ext",
> > |               bc->cfg.extmodem ? "ext" : "int", bc->cfg.fclk, bc->cfg.bps,
> > |               bc->cfg.loopback ? ",loopback" : "");
> > 
> > Note that this data is copied out to userspace with:
> > |       if (copy_to_user(data, &hi, sizeof(hi)))
> > ... however, the data was also copied FROM the user here:
> > |       if (copy_from_user(&hi, data, sizeof(hi)))
> > 
> > Considering the above, a suitable replacement is strscpy_pad() as it
> > guarantees NUL-termination on the destination buffer while also
> > NUL-padding (which is good+wanted behavior when copying data to
> > userspace).
> > 
> > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> > Link: https://github.com/KSPP/linux/issues/90
> > Cc: linux-hardening@vger.kernel.org
> > Signed-off-by: Justin Stitt <justinstitt@google.com>
> 
> Thanks!
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>

Likewise, thanks. I prefer this over v1.

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH v2] hamradio: replace deprecated strncpy with strscpy_pad

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 16 Oct 2023 18:42:42 +0000 you wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> We expect both hi.data.modename and hi.data.drivername to be
> NUL-terminated based on its usage with sprintf:
> |       sprintf(hi.data.modename, "%sclk,%smodem,fclk=%d,bps=%d%s",
> |               bc->cfg.intclk ? "int" : "ext",
> |               bc->cfg.extmodem ? "ext" : "int", bc->cfg.fclk, bc->cfg.bps,
> |               bc->cfg.loopback ? ",loopback" : "");
> 
> [...]

Here is the summary with links:
  - [v2] hamradio: replace deprecated strncpy with strscpy_pad
    https://git.kernel.org/netdev/net-next/c/d4b14c1da5bf

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html